Twist drill sharpening attachment for tool grinder



:Feb. 12?, 1957 c. K. JENSCH I TWIST DRILL SHARPENING ATTACHMENT F FiledApril 28 1954 OR TOOL GRINDER 3 Sheets-Sheet '1 INVENTOR.

.kfevsc Feb. 12, 1957 c. K. JENSCH 2,780,394.

TWIST DRILL SHARPENING ATTACHMENT FOR TOOL GRINDER Filed April 28, 19543 Sheets-Sheet 2 INVENTOR.

Feb. 12, 1957 c. K; JENSCH TWIST DRILL SHARFENING ATTACHMENT FOR TOOLGRINDER ,Filed April 28, 1954 s Sheets-Sheet s INVENTOR.

United tates Patent TWIST DRILL SHARPENING ATTACHMENT FOR TOOL GRINDERClyde K. Jensch, Elm Grove, Wis., assignor to Nordberg ManufacturingCompany, Milwaukee, Wis., a corpora- I tion of Wisconsin ApplicationApril 28, 1954, Serial No. 426,157

4 Claims. (Cl. 51----96) My invention relates to an improvement in toolsharpeners and is particularly directed to a new and improved apparatusfor sharpening twist drill bits.

A major purpose of the present invention is theprovision of a sharpeningattachment for twist drills wherein the attachment is so arranged withrespect to the peripheral surface of a grinding wheel as to enable anoperator properly to sharpen a twist drill.

One object of the present invention is to provide a guiding assembly inwhich a twist drill bit to be sharpened or surfaced is manually moved toa predetermined position or at a predetermined angle across the movingperipheral surface of one or more grinding wheels.

Another object of the present invention is the provision of a new andimproved apparatus for sharpening twist drill bits which can be simplyadjusted or regulated to accommodate various sizes of twist drill bitsfor sharpening.

Another purpose is the provision of a new and improved sharpeningapparatus for twist drill bits in which the required cutting surface forthe bit is generated automatically by moving the bit through apredetermined path with relation to the peripheral surface of a rotatinggrinding wheel.

Other purposes will appear from time to time in the course of theensuing specification and claims.

I illustrate the invention more or less diagrammatically in theaccompanying drawings wherein:

Figure 1 is a perspective view of the grinding assembly of the presentinvention;

Figure 2 is a plan view partly in section of the attachment shown inFigure 1;

Figure 3 is a side elevation view of the attachment shown in Figure 2;

Figure 4 is an end view of the attachment shown in Figure 2 lookingtoward the grinding wheel shown in Figure 2;

Figure 5 is a plan view of certain supporting elements for theattachment shown in Figure 1;

Figure 6 is a view similar to Figure 3 but showing another operativeposition of the elements;

Figure 7 is a detail view of the gauging elements em ployed in thepresent invention;

Figure 8 is a detail view of one of the elements used in the presentinvention; and

Figure 9 is a side elevation view illustrating the relation of a drillbit to the grinding wheel.

Twist drill bits have a body portion which is formed into a plurality ofspiral portions which are separated by spaces or flutes throughout asubstantial portion of the bit, The spiral portions terminate in endsurfaces which are inclined to the axis of the bit and which merge intothe tip of the drill bit. A cutting edge for the drill bit is formed oneach of these surfaces. During rotation of the bit, the cutting edge isthe leading edge of the surfaces. Each of these cutting edges extendsgenerally from the tip of the drill bit to the outer peripheral surfaceof the spiraled bit portion.

These drill bits are designed so as to have a particular angle formedbetween the opposed cutting edges or between the cutting edge and theaxis of the bit. It is highly important to maintain this angle intactwhenever the drill bit is sharpened. Each of the end surfaces also has atrailing edge or heel. The trailing edges, however, have a smaller angleof inclusion with the axis of the drill bit than the included anglebetween the cutting edge and that axis. The particular apparatus shownand described herein is particularly adapted to maintain the correctincluded angle between the cutting edge and the axis of the drill bitand to also maintain the correct included angle between the trailingedge or edges and the axis of the drill bit during the sharpeningoperation.

Referring specifically now to the drawings and in the first instance toFigure 1, 10 represents a grinding wheel which is mounted for rotationon a frame 10a. 11 is the customary guard for the grinding wheel 10. Anysuitable means, such as the belt and pulley assembly 12, may be employedto rotate the grinding wheel. The belt and pulley assembly 12 may bepowered by any suitable prime mover, such as an internal combustionengine.

A pair of spaced, generally parallel rods 13 and 14 are formedintegrally with a supporting member 15, which is positioned adjacent theperipheral surface of the grinding wheel. The rods 13 and 14 are adaptedfor reception within correspondingly spaced bores, formed in frameportions 16 and 17. Any suitable means, such as the setscrews 16a and17a, may be employed to lock the rods at a predetermined position withinthe bores and thus hold the supporting member 15 in a predeterminedspaced relation to the surface of the grinding wheel 10.

Designated generally at 15a are a plurality of roller members which areadapted to receive and support a car riage of a tool holder. The rollersform no part of the present invention. This form of support, which iscarried by the grinding wheel assembly, is known to the art and it isillustrated as one form of convenient support for the present attachmentinvention. The present invention makes use of this form of supportingmember in an assembly for sharpening twist drill bits.

A plate 18 is joined to the supporting member 15. The plate 18 has apair of spaced bores 19 and 20 formed therein for the reception of apair of correspondingly spaced rods 21 and 22 of an adapter 23 for atwist drill bit holder (Figure 8). The adapter 23 includes a sleeve 24which extends generally in the direction of the peripheral surface ofthe grinding wheel 10. It may be inclined slightly to the axis of thegrinding wheel 10 as will be seen in Figure 2 and also inclined to theplane of the grinding wheel 10. By the term plane of the grinding wheel1%, I mean that plane which is perpendicular to the axis of rotation ofthe wheel 10 and that which passes through the middle of the peripheralsurface of the wheel.

A twist drill bit holder 25 includes a rod 26, formed unitarily with aplate like portion 25a, and insertable within the sleeve 24. The holderincludes a second portion 251: pivotally connected with the rod 26 as at28 and a generally elongated groove 29 formed therein. The axis of thegroove 29 is disposed in the same general plane as the axis of the rod26. The groove 29 is adapted to receive a twist drill bit 36. Anadjusting screw 31 is mounted in one end of the portion 25b and has oneend portion bearing against the end portion of a twist drill bit 39lying in the groove 29. Indicated at 32a is a lock nut to. hold thescrew 31 at any desired position of adjustment.

The holder also includes a member 33 which is hingedly mounted on theportion 25b as at 34 to clamp the drill bit 30 in the desired positionof adjustment. Any suitable hockingmeans 35- (Fig. '9) may be carried bythe member 25b and engageable with the member. 33- to hold the member 33in its'closed position. The member 33 carries anadjustable abutment 33a(Fig. 4), which cooperates with the groove 29 to hold the bit in anydesired position of adjustment.

According to the principles of the invention, the axis of the sleeve 24,axis of thedrill bit 30 and extension of the drill bit 30 with relationto the holder 25 and wheel 1 are soarranged that in the initial ornormal position, the axis of the drill bit; is inclined to the plane ofthe grinding wheel but spaced fromtthe peripheralsurface of the grindingwheel 10. In this. position it is important thatthe drill bit end faceopposed to the surface of the grinding wheel has the cutting edge.thereof disposed upwardly and away from the grinding wheel. The drillbit must also be rotated to an initial position such that duringrotation about the axis of the sleeve 24 the trailing edge of the endface will first make contact with the wheel to form an angle between theaxis of the bit and the line of intersection of the end face with thewheel less than the desired angle of the cutting edge with the axis.Thus, as theholder is rotated about the axis of the sleeve 24, thetrailing edge of that end face will first make contact with theperipheral surface of the grinding wheel and the end face will be groundto the correct configuration.

As the holder is rotated upwardly, from the position shown in Figure 1,about the axis of the sleeve 24, the grinding wheel makes progressivecontact with the entire end face of the drill hit. As the holder isrotated, and. as material is removed from the end face, the line ofintersection between the grinding wheel and the end face movesdownwardly on the grinding wheel to a point Where the angle formedbetween the axis of the drill bit and the line of intersection is equalto the desired angle of inclusion between the cutting edge and the axisof the drill bit. The invention takes advantage of the curvature of theperipheral grinding surface to form both the correct cutting angle ofthe bit and an end face which falls away from the cutting edge.

Suitable locking means designated generally at 36 and 37 may be employedto maintain the correct included angle between the axis of the sleeve 24and the axis of the drill bit 39. As shown, the locking means 36 isadapted to lock the holder 25 at the proper position for a /8" drill bitand A drill bit and the locking means 37 may be employed to lock theholder 25 at the proper position for a 9 drill bit. The bores in theplate 25a are spaced a smaller distance apart than the spacing of thepins 36 and 37 so that. only one ofthe pins may be engaged at a singletime. The spacing corresponds to a slight angular difference between theaxis of the sleeve and the axis of the; bit for the various sizes ofbits. For convenience, I have-shown the locking means in the form ofpins selectively received within spaced bores formed in the portion-25a.

The invention includes gauging means for setting up the proper extendedposition of the drill bit within the holder and to also set up theproper angular position of the drill bit within the holder. The gauging.means l1]? cludes a bracket 33 pivotally mounted upon the portion 2512as at 39. The bracket includes a portion 4% adapted to extendtransversely of the axis of the drill bit 30. Indicated generally at 41,42 and 43 are individual flute positioners each of which is pivotallymounted upon the transverse portion 40 as at 44. As shown, these flutepositioners 41-, 42 and 43 are for use with 91 /2" and drillsrespectively. As shown, the fiute positioners are=positioned so thatwhen the junction of the cutting edge and peripheral surface of thedrill bit indicated at 45 are aligned with the flute positioner, thedrill bitisat its proper extended position. Each of the flutepositioners includes a lower surface 41a, 42a and 43a. These surfacesare adapted to rest upon the opposite edges'of the flutes in the drillbit. When the drill bit is in its proper extended position, the operatorrotates the drill bit until the gauging edge of the particular flutepositioner for the particular drill bit contacts the edge at each sideof the flute. The drill bit is then in its proper angular position forthe sharpening operation.

In use, the flute positioners which are not employed for the particulardrill bit are swung out of position and held there by means ofany-suitable locking pins or screws 46 (Fig. 9).

After the drill bit is correctly positioned, the flute positioners,along with thebracket, are swung tothe inoperative position about thepivot 39.

Whereas I have shown and described an operative form of my invention, Iwish it to be understood that this showing and description is to betaken in an illustrative or diagrammatic sense. only. There are manymodifications of the invention which will fall within the scope andspirit of the invention which will be apparent to those skilled in theart. The scope of the invention, therefore, should be limited only bythe scope of the hereinafter. appended claims.

The. use and' operation of my invention are as follows:

I disclose a method and an apparatus for sharpening twist drill bitswhich requires only a simple movement for the sharpening cycle. Thetwist drill bit is initially positioned with its axis. inclined to thegeneral plane of the grinding wheel. In this initial position thecutting tip or end' of the bit is spaced from .the peripheral surface.of the grinding wheel and the trailing edge or heel of the end surfaceof the bit is closest to the grinding wheel.

The bit is then bodily rocked about an axis (as defined by the axisofthe. sleeve 24) which is located in the same plane as the axis of thebit but inclined thereto and. inclined to the. general plane of thegrinding wheel. The bit isrocked in a direction such as to bring the endface of the cutting tip of the bit into contact with the peripheralsurface of the grinding wheel.v As the bit first makes contact with thegrinding wheel and as it moves through the sharpening cycle it describesgenerally a helical path of intersection between the end surface and thegrinding wheel and grinds the end face to the proper configuration. Thuswith a simple rocking movement the operator or person performing, themethod can sharpen the bit.

The attachment has been found particularly advantageous in connectionwith sharpening of twist drill bits with an included angle on the orderof degrees between the cutting edges of the bit.

When the attachment is used. the holder is first inserted in the sleeve24 and a drill bit is inserted in the groove 29. Assuming, for example,that the operator wishes to sharpen a /2. drill bit, he moves the holderabout the pivot 28 and engages the locking means 36. The gauge and the.bracket are swung to the position indicated in Figure 2 and theflutepositioner 41 is positioned transversely of the groove 29. Theadjustment screw 31 is rotated until the drill bit moves to its properextended position. The drill bit is then rotated to a position where thelower surface 41a of the flute positioner 41 contacts the edge at eachside of the flute of the bit.

After thus positioning the drill bit, the operator rotates theholder 25about the axis of the sleeve 24. During this rotational movement, theend face of the drill bit contacts the peripheral surface of thegrinding wheel and grinds the end surface, forming a sharp cutting edgebetween the end face and the flute. The operator then returns the holderto the initial inoperative position. The clamping means for the drillbit may then be loosened and the bit rotated to present theother face ofthe drill bit. for asimilar sharpening operation.

I claim:

g 1. A twist drill bit sharpening assembly including a grinding wheeland means for rotating it about a preeyscreoa determined axis, a supportpositioned adjacent said wheel, a twist drill bit holder includingpivotally connected portions, one of said portions including a rodinsertable in a sleeve on said support, said sleeve having its axisinclined to the general plane of the grinding wheel and extending towardthe peripheral surface of said wheel, the other portion of said holderhaving a trough adapted to receive a twist drill bit, the axis of saidtrough lying in the same plane with the axis of said rod, meanscooperating with said trough to hold a twist drill bit therein 7 at apredetermined position, means cooperable with said portions for holdingthe axis of said trough at a predetermined inclination to the axis ofsaid rod and a gauging element pivotally mounted on a bracket andpresenting a surface extending perpendicular to the axis of said trough,said surface being adapted for contact with opposed edges of the fluteof a drill bit in said trough, said bracket being pivotally mounted onsaid other portion.

2. The assembly set forth in claim 1 wherein said looking means includespins carried by said second named portion and selectively insertable inspaced apertures in said first named portion.

3. The assembly set forth in claim 1 wherein said sleeve is removablymounted on said support.

4. The assembly set forth in claim 1 characterized by including aplurality of gauging elements carn'ed by said bracket portion, eachelement having a surface alignable with opposed edges of a drill bitflute carried by said trough, each of said elements being movable intoand out of contacting relation with a drill bit positioned in saidtrough.

References Cited in the file of this patent UNITED STATES PATENTS 29,433 Smith et al May 27, 1884 622,212 Dutton Apr. 4, 1899 643,703 WhiteFeb. 20, 1900 690,389 Chandler M Jan. 7, 1902 743,033 Ridderhof Nov. 3,1903 1,093,028 Bogart Apr. 14, 1914 1,106,692 Wincrantz Aug. 11, 19142,511,055 Ganz June 13, 1950 2,583,159 Swanson Ian. 22, 1952 2,607,172Roulle Aug. 19, 1952 2,632,983 Kapnick Mar. 31, 1953 FOREIGN PATENTS236,272 Switzerland June 1, 1945

